2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures
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Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology<br />
P94 ECOTOxICOLOGICAL EVALuATION OF<br />
ThE SLuDGES FROM wASTE wATER<br />
TREATMENT PLANTS<br />
HELEnA ZLáMALOVá GARGOŠOVá, LUCIE<br />
HELLInGEROVá and MILADA VáVROVá<br />
Institute of Chemistry and Technology of Environmental Protection,<br />
Faculty of Chemistry, Brno University of Technology,<br />
Purkyňova 118, 612 00 Brno, Czech Republic,<br />
zlamalova@fch.vutbr.cz<br />
Introduction<br />
The tendency to improve the water quality in the Czech<br />
Republic is linked with building up new waste water treatment<br />
plants (WWTP), what results in growing production of<br />
sewage sludges. Multi-purpose way for efficient utilization or<br />
sludge disposal hasn’t existed till now.<br />
Sewage sludges are very rich in nutrients and organic<br />
matter. This makes the spreading of this kind of waste on<br />
land as a fertilizer or an organic soil improver very suitable.<br />
Unfortunately, the sludge tends to concentrate heavy metals<br />
and organic compounds present in waste waters. The Sewage<br />
Sludge Directive (86/278/EEC) regulates sludge use in such<br />
way to prevent harmful effects on soil, vegetation, animals<br />
and man. In the Czech Republic almost one third of sewage<br />
sludges ends as a waste; this could be hazardeous. In Europe<br />
hazardous wastes are classified by 14 criteria including<br />
ecotoxicity (H 14). Environmental ecotoxicology deals with<br />
the potentially harmful effects of chemicals and wastes on<br />
organisms. For this purpose various testing organisms and<br />
various type of bioassays are used.<br />
The aim of our study was the ecotoxicological testing of<br />
sewage sludges from different waste water treatment plants<br />
by selected ecotoxicity tests with respect to their intended<br />
use. We used following organisms: crustacea Daphnia magna<br />
and Thamnocephalus platyurus and seeds of terrestrial plant<br />
Sinapis alba. The values of 24h-LC50 and 48h-LC50 obtained<br />
for Thamnocephalus platyurus and Daphnia magna and<br />
72h-IC50 values gained for Sinapis alba are the basic data for<br />
the ecotoxicological assessment of the sewage sludges and<br />
for their classification following the Czech legislation 1,2 .<br />
Experimental<br />
Samples of sewage sludges from high-capacity municipal<br />
WWTP, situated in Brno, Modřice and from small WWTP<br />
in Veterinary and Pharmaceutical University Brno were<br />
evaluated. From WWTP Brno, Modřice following sewage<br />
sludges were tested:<br />
•<br />
•<br />
•<br />
anaerobic stabilized sewage sludges (AS)<br />
dewatered anaerobic stabilized sewage sludges<br />
(DWAS)<br />
dessicated anaerobic stabilized sewage sludges (DSAS)<br />
From local WWTP in Veterinary and Pharmaceutical<br />
University Brno primary sludges were tested (PS).<br />
s529<br />
S a m p l e s P r e p a r a t i o n<br />
All samples were collected in pure plastic bottle and untill<br />
testing stored in the dark at 4 °C for less than four days prior<br />
the bioassay experiment. Samples were dried at temperature<br />
105 ± 5 °C and sludge dry residue was determinated gravimetrically.<br />
Two types of water leaches were prepared from<br />
studied sewage sludges. The first batch of samples was prepared<br />
in accordance with Czech legislation; the samples were<br />
mixed in ratio 1 : 10 (sludge dry residue: deionised water).<br />
The second one was diluted with deionised water to have<br />
the same dry matter content as anaerobic stabilized sewage<br />
sludges from WWTP Modřice (3.89 %). Sample tubes filled<br />
with defined quantity of sample and water were shaken at<br />
5–10 rpm (revolutions per minute) for 24 hour at temperature<br />
15–25 °C. After centrifugation the leaches supernatants were<br />
removed and filtered using paper filter (5 μm). To assure suitable<br />
surroundings for each testing organism the supernatants<br />
were enriched by adding specific amounts of salts following<br />
OECD Guidelines 3,4 .<br />
P r i n c i p l e o f E c o t o x i c o l o g i c a l<br />
T e s t s<br />
The general principle of ecotoxicological tests is the<br />
determination of effective concentration (EC50), eventually<br />
lethal concentration (LC50) or inhibition concentration<br />
(IC50). These concentrations of tested compound (substance,<br />
sewage water or leaches of sewage sludges) cause the mortality<br />
of 50 % of testing organisms or 50% inhibition of growth<br />
rate in relation to control tests. The organisms are exposed<br />
to the test substance for a period of 24, 48, and 72 hours in<br />
agreement with requirements of a given test. At least five<br />
test concentrations should be used. A stepwise procedure<br />
involves three steps: the preliminary test, the confirmatory<br />
test and the definitive test. The confirmatory test confirms or<br />
disconfirms results of limit test. In preliminary test undiluted<br />
sewage sludges leaches are used. If results of preliminary<br />
test indicate possible ecotoxicity the definitive test follows.<br />
The highest concentration in definitive test should preferably<br />
result in 100% immobilization (mortality or inhibition) and<br />
the lowest concentration tested should preferably give no<br />
observable effect.<br />
A p p l i c a t i o n o f E c o t o x i c i t y T e s t s<br />
f o r S e w a g e S l u d g e s E v a l u a t i o n<br />
Testing organisms (Daphnia magna, Thamnocephalus<br />
platyurus, Sinapis alba.) were used in preliminary test with<br />
raw water sewage leaches (WSL) and in definitive tests with<br />
various testing concentrations of WSL; 50, 100, 200, 500,<br />
700 ml dm –3 . Under the same conditions tests with control<br />
group of the same organisms in standard freshwater but<br />
without WSL were conducted.<br />
The Daphtoxkit FTM makes use of the dormant eggs<br />
of the crustaceans Daphnia magna, which are protected by<br />
chitinous capsule called ephippium. Ephipia can be stored<br />
for long time without losing their viability. When the testing<br />
organisms are needed it is necessary to put chitinous capsule